In a prior cutterhead disclosed in U.S. Pat. No. 4,347,882, the core of the cutterhead has a substantially rectangular cross-section, but the contact surface for the pressure plate is raised somewhat with respect to the support surface for the cover portion and is parallel thereto. The pressure plate is pressed onto the support surface by means of screws screwed centrally into the core. The pressure plate together with its free end and an adjacent surface running parallel to the contact surface for the pressure plate forms a slot. The cutting blade is inserted in this slot so that it is positioned in the desired position by positioning ribs and is secured by the clamping force exerted by the pressure plate. However, on loosening the screws securing the pressure plate, the blade can be drawn out of the slot in the axial direction of the cutterhead, or can be inserted in the slot. The arcuate cover portion rests with its one axially directed end face on the support surface of the core and with its other, radially directed end face on the radial outer end of the pressure plate. With the screws screwed into the core, the cover portion is pressed against said core and in this way is held in position. As cutting blades are provided on diagonally facing sides of the core, this leads to a cross-section of the cutterhead formed from core, pressure plates and cover portions, which is substantially circular and only has axially directed grooves in the vicinity of the projecting length of the cutting blade over the circumference of the circular cross-section.
In the case of the above cutterhead, manufacture and assembly without out-of-balance occurring can be difficult, because as a result of the unavoidable tolerances of the screws and particularly the screws used for fixing the covers, it is not always possible to achieve a precise positioning of the covers on the core. However, if the covers are not held precisely in the correct position with respect to the core, there is a change to the mass distribution with respect to the rotational axis of the core, and consequently to the cutterhead, so that an unbalanced condition occurs.